> ## Documentation Index > Fetch the complete documentation index at: https://developer.sandbox.co.in/llms.txt > Use this file to discover all available pages before exploring further. # Verify OTP > Verify OTP to authenticate tax payer. This API will start a session and provide access valid for 6 hrs. Returns date timestamp of expiry of session. **Prerequisites:** You must enable API access to get access to GST APIs. If not done already, [enable API access](/api-reference/gst/compliance/guides/taxpayer/authentication/enable_api_access). ## OpenAPI ````yaml api-reference/gst/compliance/openapi.json POST /gst/compliance/tax-payer/otp/verify openapi: 3.0.1 info: title: compliance description: >- **GST Compliance API** enables businesses to automate compliance requirements like [Taxpayer verification](https://developer.sandbox.co.in/reference/search-gstin-api), [GSTR Filing](https://developer.sandbox.co.in/reference/gst-taxpayer-authentication), [Generating E-Invoices](https://developer.sandbox.co.in/reference/e-invoice-authentication-api), and [E-Way Bills](https://developer.sandbox.co.in/reference/e-way-bill-authentication-api).We provide these APIs from GSTN-authorised GST Suvidha Providers, handling the encryption-decryption and signing so you don't have to handle the complexities. version: 1.0.0 servers: - url: https://api.sandbox.co.in - url: https://test-api.sandbox.co.in security: [] tags: - name: Public - name: Taxpayer - name: Taxpayer Auth - name: Returns - name: GSTR-1 Documents - name: File GSTR-1 - name: GSTR-2A Documents - name: GSTR-2B Document - name: File GSTR-3B - name: GSTR-4 - name: File GSTR-9 - name: Invoice Management System - name: GSTR-1A Documents - name: File GSTR-1A - name: Ledgers - name: e-Invoice - name: Sales e-Invoices for return period - name: Purchase e-Invoices for return period - name: Front Office Notices - name: Front Office - name: AATO - name: e-Invoice1 - name: Authentication - name: e-Invoice12 - name: E-Way Bill - name: E-Way Bill1 - name: Authentication1 - name: Consignor - name: Consolidated E-Way Bill - name: Multi-Vehicle Movement - name: Consignee - name: Transporter - name: Consolidated E-Way Bill1 - name: Multi-vehicle Movement - name: Common paths: /gst/compliance/tax-payer/otp/verify: post: tags: - Taxpayer - Taxpayer Auth summary: Verify OTP description: >- Verify OTP to authenticate tax payer. This API will start a session and provide access valid for 6 hrs. Returns date timestamp of expiry of session. operationId: verifyOtp parameters: - name: otp in: query description: One time password required: true example: 575757 schema: type: integer format: int32 example: '575757' - name: authorization in: header description: JWT access token required: true example: '{{access_token}}' schema: type: string - name: x-source in: header description: 'Source. Possible Values: primary (default) or secondary' required: false example: primary schema: type: string default: primary example: primary - name: x-api-key in: header description: API key for identification required: true example: '{{api_key}}' schema: type: string - name: x-api-version in: header description: API version required: false example: '' schema: type: string default: 1.0.0 requestBody: content: application/json: schema: type: object required: - username - gstin properties: username: type: string description: Username as per GST portal gstin: type: string description: GSTIN of the taxpayer examples: 200 Success: value: username: TN_NT2.2477 gstin: 33ABKCS2033B1ZW summary: 200 Success AUTH4033 Invalid session: value: username: globex.edu.co gstin: 23ABCCQ2000E000 summary: AUTH4033 Invalid session responses: '200': description: AUTH4033 Invalid session / 200 Success content: application/json: schema: type: object properties: code: type: number example: 200 data: type: object properties: access_token: type: string example: >- eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ0YXhwYXllci1zZXNzaW9uIiwiZ3N0aW4iOiIyNEFCS0NTMjAzM0IxWlYiLCJpYXQiOjE3MTI5NDQxMDAsImV4cCI6MTcxMjk0NzcxMX0.sandbox-signature error: type: object properties: error_cd: type: string example: AUTH4033 message: type: string example: Invalid Session session_expiry: type: number example: 1712947711000 status_cd: type: string example: '0' token_expiry: type: number example: 1712947711000 timestamp: type: number example: 1763446641000 transaction_id: type: string example: 1ad1d698-499e-4b10-a44a-fecba43babbb examples: 200 Success: summary: 200 Success value: code: 200 data: access_token: >- eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ0YXhwYXllci1zZXNzaW9uIiwiZ3N0aW4iOiIyNEFCS0NTMjAzM0IxWlYiLCJpYXQiOjE3MTI5NDQxMDAsImV4cCI6MTcxMjk0NzcxMX0.sandbox-signature session_expiry: 1712947711000 status_cd: '1' token_expiry: 1712947711000 timestamp: 1712926110000 transaction_id: f6a85bd7-6d53-4e60-b4a7-480d3738ff0c AUTH4033 Invalid session: summary: AUTH4033 Invalid session value: code: 200 data: error: error_cd: AUTH4033 message: Invalid Session status_cd: '0' timestamp: 1763446641000 transaction_id: 1ad1d698-499e-4b10-a44a-fecba43babbb headers: {} '500': description: Invalid GSTIN pattern content: application/json: schema: type: object properties: code: type: number example: 422 message: type: string example: Invalid GSTIN pattern timestamp: type: number example: 1763446641000 transaction_id: type: string example: 21c38e93-b4df-4266-84ca-28885be68d1e examples: Invalid GSTIN pattern: summary: Invalid GSTIN pattern value: code: 422 message: Invalid GSTIN pattern timestamp: 1763446641000 transaction_id: 21c38e93-b4df-4266-84ca-28885be68d1e headers: {} deprecated: false security: [] ````